Fig. 6: FRAP analysis of FTLD P301L mutant Tau shows slow recovery, but the deletion of the MTBD increases Tau mobility and reverts Fyn-mEos2 lateral trapping in neurons.

A Representative image of a hippocampal neuron transfected with Tau-P301L-GFP that has an intracellular Tau droplet. White box outlines indicate the cytosolic region and droplet-containing region where FRAP was performed, shown at a higher magnification in B and C, respectively. B, C Series of images acquired during FRAP analysis (prebleach 0 s, postbleach 2.59 s, 3.62 s and 51.23 s) of Tau-P301L-GFP in B the cytosol or C droplet outlined in A. D Plot of Tau-P301L-GFP FRAP analysis in the cytosol and droplet, as indicated. E Representative image of a hippocampal neuron transfected with Tau-P301L-GFP. The white box outline denoted by i is shown magnified below in (i). F, G Series of images acquired during FRAP analysis (prebleach 0 s, postbleach 3.12 s, 4.17 s and 45.35 s) of F Tau-P301L-GFP or G ΔTau74-GFP within dendritic spines. H Average plot of FRAP analysis of Tau-P301L-GFP or ΔTau74-GFP in dendritic spines, as indicated. I Quantification of the mobile fraction of the FRAP curves in H. J Representative epifluorescence images of mCardinal co-expressed in hippocampal dendrites with Fyn-mEos2 and Tau-P301L-GFP. White box outlines are shown at a higher magnification on the right with Tau-P301L-GFP epifluorescence and corresponding Fyn-mEos2 diffusion coefficient maps shown. Note that hotter colours within the diffusion coefficient map designate regions of lower mobility. K Representative epifluorescence images of mCardinal co-expressed in hippocampal dendrites with Fyn-mEos2 and ΔTau74-GFP. White box outlines are shown at a higher magnification on the right with ΔTau74-GFP epifluorescence and corresponding Fyn-mEos2 diffusion coefficient maps shown. Note that hotter colours within the diffusion coefficient map designate regions of lower mobility. L Mobility of Fyn-mEos2 co-expressed with Tau-P301L-GFP or with ΔTau74-GFP in hippocampal neurons indicated as the MSD (µm²) curves over time (0.14 s). M Corresponding AUC (µm² s) of the graphs in L. Error bars are standard errors of the mean (SEM). Mean ± SEM values in H, I were obtained from hippocampal neurons transfected with Tau-P301L-GFP (N = 18) or ΔTau74-GFP (N = 12). Mean ± SEM values in L, M were obtained from hippocampal neurons co-transfected with mCardinal, Fyn-mEos2 and Tau-P301L-GFP (N = 13) or mCardinal, Fyn-mEos2 and ΔTau74-GFP (N = 14). Statistical comparison in I and M were performed using the unpaired Welch’s t-test. The specific adjusted p values accounting for multiple comparisons are reported when the data are considered significantly different (p < 0.05).